Optimization Of Magnetic Damping And Design Of Electric Damping For Torsion Pendulum

Because of high detection sensitivity in twist degree of freedom,torsion pendulum is widely applied for kinds of precise weak force test experiments.In high-precision ground gravitational experiments,we usually use torsion pendulum which is composed of suspension fiber and a test mass to response the interaction between an attraction mass and the test mass.But in these experiments,the swing modes of the torsion pendulum will lead to "Abnormal Mode" and bring errors.To suppress the "Abnormal Mode",we usually use passive damping system such as the magnetic damping to suppress the swing mode by eddy current loss.However,the magnetic damping system will lead to a lot of restrictions.In the measurement of Newtonian gravitational constant G with angular acceleration feedback method,the traditional magnetic damping system will contribute one of the largest errors.In order to effectively suppress the "Abnormal Mode" as well as decrease the error from the damping system,we need to optimize the existing magnetic damping system or present a new suppressed scheme for the "Abnormal Mode".As a consequence,it will be significance for all kinds of precision weak force measurement experiments based on the torsion pendulum to investigate the damping system and decrease its error.In this thesis,we firstly researched the magnetic damping,cleared and quantified the relationship between damping force and swing speed during damping the swing mode.By optimizing all design parameters of the magnetic damping system,in the measurement of Newtonian gravitational constant G with angular acceleration feedback method,the error originating from the magnetic damping system is controlled within 10 ppm on the premise of guarantee the damping effect.In order to further decrease the error caused by damping system,and then a new electrical damping scheme was presented.We calculate and simulate for two kinds of electrical damping system with a rectangular test mass or a cylindrical test mass.Research results show that the electrical damping system can change two-stage pendulum into single stage pendulum.In this way,we can eliminate the error from damping system in the measurement of Newtonian gravitational constant G with angular acceleration feedback method without losing its capability of damping swing motion.We also present the error analysis and the feasibility proof about the electric damping system to provide a reliable theoretical basis and guidance for the design of damping system of the "Abnormal Mode" in experiments.